Adsorption behavior of modified Iron stick yam skin with Polyethyleneimine as a potential biosorbent for the removal of anionic dyes in single and ternary systems at low temperature

Removal of food dyes using biological materials via adsorption: A review

It is alarming that synthetic food dyes (FD) are widely used in various industries and that these facilities discharge their wastewater into the environment without treating it. FDs mixed into industrial wastewater pose a threat to the environment and human health. Therefore, removing FDs from wastewater is very important. This review explores the burgeoning field of FD removal from wastewater through adsorption using biological materials (BMs). By synthesizing a wealth of research findings, this comprehensive review elucidates the diverse array of BMs employed, ranging from algae and fungi to agricultural residues and microbial biomass. Furthermore, this review investigates challenges in practical applications, such as process optimization and scalability, offering insights into bridging the gap between laboratory successes and real-world implementations. Harnessing the remarkable adsorptive potential of BMs, this review presents a roadmap toward transformative solutions for FD removal, promising cleaner and safer production practices in the food and beverage industry.

Facile synthesis of high-efficiency magnetic graphitic carbon nitride adsorbents for the selective removal of hazardous anionic dyes in wastewater

A novel composite adsorbent was successfully prepared by a simple impregnation method. The prepared adsorbent not only exhibits ultra-efficient and selective removal of anionic dyes, but also shows excellent performance in practical water samples.

Facile transformation of carboxymethyl cellulose beads into hollow composites for dye adsorption

Novel millimeter hollow microspheres were fabricated from carboxymethyl cellulose microspheres and polyethyleneimine using glutaraldehyde as a crosslinking agent. The hollow microspheres prepared with different polyethyleneimine usages and different polyethyleneimine treatment time were investigated deeply and characterized via SEM-EDX, FT-IR, and BET surface area analysis. It was shown that polyethyleneimine could break the coordination bonds between the carboxyl and Al (III) in carboxymethyl cellulose microspheres, leading to the formation of hollow structures. Most importantly, the usage and treatment time of polyethyleneimine can distinctly tailor the structure of the carboxymethyl cellulose microspheres, resulting in the formation of different hollow microspheres with varied shell thickness and size. Most importantly, we found that the prepared hollow microspheres have excellent adsorption performance toward targeted methyl blue under testing conditions. By virtue of the large accessible amount of -NH₂ groups and its unique hollow structure, this type of millimeter hollow microspheres have broad application prospects in the treatment of emerging contaminants in wastewater.

Improving the resistance of Anammox granules to extreme pH shock: The effects of denitrification sludge EPS enhanced by a fluctuating C/N ratio cultivation on granules

This study investigated the effects of denitrification sludge EPS enhanced (DS-EPS_CN) by a fluctuating carbon and nitrogen ratio (C/N) cultivation strategy on the properties of Anammox granules under extreme acid or alkaline shock. The results showed that the DS-EPS_CN significantly improved the nitrogen removal performance of low-density Anammox granular sludge (Granules-_L) and high-density Anammox granular sludge (Granules_-H) under extreme acid shock (pH 5.0). The contents of high-molecular-weight substances (such as aromatic proteins and polysaccharides) in the DS-EPS_CN rose markedly, contributing to a substantial increase in the flocculation efficiency under acidic conditions and increasing the granule stability. In addition, abundant amounts of N-butyryl-dl-homoserine lactone (C4-HSL) and N-hexanoyl-dl-homoserine lactone (C6-HSL) in the DS-EPS_CN promoted the granule activity. However, under extreme alkaline shock (pH 10.5), the flocculation efficiency of the DS-EPS_CN was poor, and the addition of DS-EPS_CN had no influence on the stability of the granules but improved the activity of the Granules_-H. The reason was that the release mechanism of the endogenous acyl-homoserine lactone (AHL) signals in the Granules_-H was activated by the exogenous C4-HSL and C6-HSL in the DS-EPS_CN under alkaline conditions, leading to increased Granules_-H activity. This research provides a novel approach to enhance the resistance of Anammox granular sludge to extreme pH shock.

Adsorption isotherm models: Classification, physical meaning, application and solving method

Adsorption is widely applied separation process, especially in environmental remediation, due to its low cost and high efficiency. Adsorption isotherm models can provide mechanism information of the adsorption process, which is important for the design of adsorption system. However, the classification, physical meaning, application and solving method of the isotherms have not been systematical analyzed and summarized. In this paper, the adsorption isotherms were classified into adsorption empirical isotherms, isotherms based on Polanyi's theory, chemical adsorption isotherms, physical adsorption isotherms, and the ion exchange model. The derivation and physical meaning of the isotherm models were discussed in detail. In addition, the application of the isotherm models were analyzed and summarized based on over 200 adsorption equilibrium data in literature. The statistical parameters for evaluating the fitness of the models were also discussed. Finally, a user interface (UI) was developed based on Excel software for solving the isotherm models, which was provided in supplemental material and can be easily used to model the adsorption equilibrium data. This paper will provide theoretical basis and guiding methodology for the selection and use of the adsorption isotherms.

Simultaneous removal of cationic and anionic dyes from aqueous solution by double functional groups modified bagasse

Double functional groups modified bagasse (DFMBs), a series of new zwitterionic groups of carboxyl and amine modified adsorbents, were prepared through grafting tetraethylenepentamine (TEPA) onto the pyromellitic dianhydride (PMDA) modified bagasse using the DCC/DMAP method. DFMBs' ability to simultaneously remove basic magenta (BM, cationic dye) and Congo red (CR, anionic dye) from aqueous solution in single and binary dye systems was investigated. FTIR spectra and Zeta potential analysis results showed that PMDA and TEPA were successfully grafted onto the surface of bagasse, and the ratio of the amount of carboxyl groups and amine groups was controlled by the addition of a dosage of TEPA. Adsorption results showed that adsorption capacities of DFMBs for BM decreased while that for CR increased with the increase of the amount of TEPA in both single and binary dye systems, and BM or CR was absorbed on the modified biosorbents was mainly through electrostatic attraction and hydrogen bond. The adsorption for BM and CR could reach equilibrium within 300 min, both processes were fitted well by the pseudo-second-order kinetic model. The cationic and anionic dyes removal experiment in the binary system showed that DMFBs could be chosen as adsorbents to treat wastewater containing different ratios of cationic and anionic dyes.

Implication for adsorption and degradation of dyes by humic acid: Light driven of environmentally persistent free radicals to activate reactive oxygen species

Humic acid (HA) was applied as the biosorbent for the adsorption and degradation of dyes in the presence of environmentally persistent free radicals (EPFRs). Scanning Electron Microscope (SEM) analysis showed that the microstructure of the HA surface and the thermal stability was analyzed by thermogravimetric analysis (TGA). Following irradiation, semiquinone EPFRs (g-factor > 2.0045) were generated on the HA surface. Both O₂ and the addition of H₂O₂ were able to promote the generation of hydroxyl and superoxide radicals for the degradation of dye in aqueous solution. Furthermore, adsorption was observed to remove large amounts of the dyes, while the instantaneous free radical degradation process reduced the dyes to the lower concentration. In addition, a linear relationship was observed between the consumption of EPFRs and dye degradation rates. In ternary systems, HA conformed to Langmuir (476.19-1250.12 mg/L) and pseudo-second-order kinetic models. This work offers new insights into HA-EPFRs and their potential applications.

Adsorption of Mixed Dye System with Cetyltrimethylammonium Bromide Modified Sepiolite: Characterization, Performance, Kinetics and Thermodynamics

In this study, sepiolite was modified by calcination (200 °C) and cetyltrimethylammonium bromide (CTMAB) treatment. Though the specific surface area sharply declined, the adsorption amount of Acid Orange II (AO), Reactive Blue (RB), Acid Fuchsin (AR) and their mixed solution were improved. The morphology of modified sepiolite showed a better dispersibility and looser structure. The adsorption performance was highly impacted by the pH condition and adsorbent dosage. The electrostatic attraction of positively charged adsorption sites on the adsorbent surface and the negatively charged anionic dye could enhance the adsorption amount especially under acid condition. The order of preferentially adsorbed dye was AO > RB > AR. The adsorption process was much correlated to the quasi-second-order reaction kinetics. The adsorption amount and equilibrium amount of single dye system, as well as in the mixed system were in accordance with the Langmuir model and extended Langmuir isotherm.

Nano-engineered Adsorbent for the Removal of Dyes from Water: A Review

Background:

The huge quantity of wastewater, containing poisonous and hazardous dyes, is released by various industries which pollute water in direct and indirect ways. Most of the dyes are a dangerous class of water contaminants which have affected the environment drastically. Some dyes such as congo red, rhodamine B, methylene blue, methyl violet, and crystal violet are a serious threat to human beings.

Remediation Method:

Numerous methods are available for the removal of dyes from water. Adsorption, being a superior and eco-friendly technique, has advantage of eliminating organic dyes because of the availability of materials as adsorbents. The inexpensive nanomaterials are a more attractive choice for remediation of various dyes due to their unique properties and offer an adequate pathway to adsorb any organic dye from water to overcome its hazardous effects on human health.

Results:

In this review, we have discussed the latest literature related to various types of synthesis, characterization and uses as adsorbent for highly adsorptive removal capacity of nanoparticles for organic dyes.

Conclusion:

Adsorption technology provides an attractive pathway for further research and improvement in more efficient nanoparticles, with higher adsorption capacity, for numerous dyes to eliminate the dyes discharged from various industries and thus reduce the contamination of water. Therefore, nanocomposites may contribute to future prospective water treatment process.

Adsorption mechanism of polyethyleneimine modified magnetic core-shell Fe3O4@SiO2 nanoparticles for anionic dye removal

In this paper, polyethyleneimine modified magnetic core-shell Fe3O4@SiO2 nanoparticles (Fe3O4@SiO2/PEI) were innovatively synthesized and investigated using various techniques such as TEM, TGA, FT-IR, XRD, VSM and XPS. The adsorption performance based on the removal of the anionic dyes Methyl orange and Congo red from aqueous solution was studied systematically. The results showed that the adsorption rate of anionic dyes MO and CR increased rapidly then decreased gradually as the pH increased, the adsorption capacity of Fe3O4@SiO2/PEI for MO was better than that for CR, and the maximum adsorption capacity for MO and CR was 231.0 mg g-1 at pH 4 and 134.6 mg g-1 at pH 6, respectively. The equilibrium adsorption capacities for MO and CR increased rapidly in the initial 40 min, and reached equilibrium in approximately 180 min, while the adsorption capacity for MB was relative low even negligible, demonstrating the strong adsorptive affinity of Fe3O4@SiO2/PEI toward anionic compounds. Both of the adsorption processes followed the pseudo-second-order kinetics model and the Freundlich isotherm model. The mechanism of adsorption was mainly related to electrostatic attraction and the number of active sites occupied by anionic dyes. This study provides valuable guidance and is an effective method for the removal of anionic dyes from aquatic environments.

Simultaneous Adsorption of Cationic Dyes from Binary Solutions by Thiourea-Modified Poly(acrylonitrile-co-acrylic acid): Detailed Isotherm and Kinetic Studies

In this study, simultaneous adsorption of cationic dyes was investigated by using binary component solutions. Thiourea-modified poly(acrylonitrile-co-acrylic acid) (TMPAA) polymer was used as an adsorbent for uptake of cationic dyes (malachite green, MG and methylene blue, MB) from aqueous solution in a binary system. Adsorption tests revealed that TMPAA presented high adsorption of MG and MB at higher pH and higher dye concentrations. It suggested that there are strong electrostatic attractions between the surface functional groups of the adsorbent and cationic dyes. The equilibrium analyses explain that both extended Langmuir and extended models are suitable for the description of adsorption data in the binary system. An antagonistic effect was found, probably due to triangular (MG) and linear (MB) molecular structures that mutually hinder the adsorption of both dyes on TMPAA. Besides, the kinetic studies for sorption of MG and MB dyes onto adsorbent were better represented by a pseudo-second-order model, which demonstrates chemisorption between the polymeric TMPAA adsorbent and dye molecules. According to experimental findings, TMPAA is an attractive adsorbent for treatment of wastewater containing multiple cationic dyes.

Novel cellulose/montmorillonite mesoporous composite beads for dye removal in single and binary systems

Fine aminated cellulose/montmorillonite mesoporous composite beads (ACeMt) were prepared as green-based adsorbent via a novel approach utilizing ultra-fine calcium carbonate as a pore-forming agent to increase the porosity and specific surface area of ACeMt. The resulting bioadsorbent was characterized by means of SEM, FTIR and BET analysis and used for dye removal. Adsorption experimental data were fitted with various isotherm and kinetic models. The results indicated that chemical adsorption was the rate-limiting step. The maximum adsorption capacities of ACeMt, better described by Langmuir model, were much higher than those of conventional adsorbents, particularly for the removal of Auramine O dye (up to 1336.2 mg/g at 55 °C). The adsorptions at equilibrium were better correlated with Redlich-Peterson model and uncompetitive Langmuir isotherm model in single and binary system, respectively. Overall, ACeMt is a promising bioadsorbent and highly efficient in the removal of dyes for water clarification.

Feasibility of industrial-scale treatment of dye wastewater via bio-adsorption technology

This review emphasizes the importance of costs in industrial-scale treatment of dye wastewater and provides a way to assess the cost-based feasibility of bio-adsorption technologies. Dye wastewater is one of the major contributors to environmental pollution. Bio-adsorption has attracted considerable attentions in dye wastewater treatment due to its technical feasibility, flexibility and operation simplicity. However, industrial-scale treatment of dye wastewater via bio-adsorption technologies remains stagnant, mainly due to high costs. So far, no review or research articles have systematically discussed the criteria for successful utilization of bio-adsorption technologies on a large scale. This review discusses the major factors affecting adsorption and desorption performance based on basic chemical and physical structures of bio-adsorbents available in literatures. A quantitative relationship has been summarized based on previous studies to assess the cost to utilize a bio-adsorption technology and serve as an access threshold for quality bio-adsorbents to be taken into real applications.

Iron-based metal–organic framework as an effective sorbent for the rapid and efficient removal of illegal dyes

A metal organic framework (MOF-235) was fabricated by a simple solvothermal method and utilized as an adsorbent for the selective removal of electron-rich conjugated dyes.

Disolved organic matter (DOM) removal from bio-treated coking wastewate using a new polymeric adsorbent modified with dimethylamino groups

In the current study a new recyclable aminated hyper-cross-linked polymeric adsorbent (A-HPA) was prepared for effective removal of DOM from BTCW. Possibly benefited from its unique structure of polystyrene matrix, sufficient aminated groups and high specific surface area, A-HPA could remove DOM from BTCW through the synergetic effect of π-π interactions, acid-base interactions and micropore filling, and exhibited the highest removal efficiency than the other adsorbents. Moreover, the exhausted A-HPA was amenable to effective regeneration by using acid and alkaline solution, allowing for repeated use with a constant removal efficiency. Field application of continuous 3-year fixed-bed runs demonstrated that A-HPA is capable of effectively removing DOM from BTCW with no significant capacity loss, and the treated effluent can be partially used as recycled water in production. All the above results demonstrated that A-HPA adsoption could serve as a good choice for the advanced treatment of bio-treated sewage effluent.